A. Field of the Invention
This invention relates to the field of bicycle handlebars. More particularly, in the preferred embodiment the invention is a strong, lightweight fiber-reinforced plastic handlebar for all-terrain bicycles (i.e."mountain bikes"). The invention includes a method for making the desired handlebar as a one-piece unit with the aid of an injection molding process.
B. The Background Art
It is desirable in the bicycle arts to replace conventional metal bicycle parts with fiber-reinforced plastic parts. In many applications, fiber-reinforced plastic parts are preferred because they typically offer lighter total weight, inherent shock absorption due to the nature of fiber-reinforced plastic materials, durability, a high-tech appearance and in some cases, lower manufacturing costs.
Due to the preferences of typical bicycle consumers, only fiber-reinforced plastic parts which conform to conventional bicycle appearance, shape, configuration, and attachment means have been commercially successful. There appear to be two reasons for this. First, bicycle consumers are often not comfortable using components that are quite different in appearance than the proven standard bicycle components. Second, bicycle components which are different in shape, configuration, or attachment points may not fit to other standard components or accessories, thus limiting their use or creating additional discomfort to the user because of the possibility of difficulty in future modifications to the bicycle.
Another preference of bicycle consumers that must be taken into consideration is to use the same number of or to use fewer components than are employed on a traditional bicycle. Therefore bicycle consumers find it undesirable to replace a single traditional metal component with two or more fiber-reinforced plastic parts. As a general matter, as total part count is reduced, reliability of the bicycle is increased and total cost is decreased.
The preference of most bicycle consumers for bicycle components of traditional shape and configuration is difficult to satisfy when providing fiber-reinforced plastic components. Typically, a traditional metal bicycle component cannot simply be reproduced as a fiber-reinforced plastic part. Such an identical reproduction typically is not structurally optimized for the material used, and thus typically does not have adequate structural integrity or strength to perform its desired function, resulting in less durability and performance than the metal part sought to be replaced. Further it is generally impossible or at least impractical to identically reproduce a metal part as a fiber-reinforced plastic part because of differences in the available manufacturing methods for metal parts compared with composite parts. Thus, fiber-reinforced plastic components must be designed to provide the desired strength characteristics for their particular application within the available manufacturing method for fiber-reinforced plastics. Such design work is complicated by the need to produce a component which has the same outward shape and configuration as the metal part which it replaces. And the design work is further complicated by the desire of bicycle consumers to utilize fiber-reinforced plastic parts that are equal to or fewer in number than the traditional metal parts that they replace.
In the prior art, the standard shape for metal handlebars for many bicycles, including mountain bikes, is that of a relatively straight tube. These tubes typically have a straight portion in the center, and two end portions which angularly diverge from the longitudinal axis of the center section by about three degrees. The tubes (by the nature of being tubes) have an interior hollow portion.
Prior art fiber-reinforced plastic handlebars typically exhibited a drastically different outward appearance, in shape, configuration, and attachment means than standard metal handlebars. Because of their atypical configuration, such handlebars did not accept standard components or accessories, to the dissatisfaction of their users. Some such handlebars incorporated a greater number of parts than prior art metal handlebars, also to the dislike of typical bicycle consumers.
U.S. Pat. No. 5,269,196 to Rafac, which is hereby incorporated by reference for the material disclosed therein, discloses an injection-molded plastic handlebar which accepts standard brake levers. The Rafac handlebar differs very substantially in shape, appearance, and configuration than typical prior art metal handlebars. The Rafac handlebar also has more parts than a standard one-piece handlebar in that the grip portions must be made separately from the central portion, and the three components later assembled into a handlebar, also contrary to the preference of bicycle consumers. While Rafac made an attempt to provide a handlebar that offers the performance of fiber-reinforced plastic, the configuration and shape that he employed, presumably to achieve what he believed to be a structurally sound handlebar, was found objectional by typical bicycle consumers.
U.S. Pat. No. 4,245,522 to Robinson, which is hereby incorporated by reference, discloses a plastic handlebar which made by assembling multiple pieces. Robinson requires non-standard brake levers and shift levers, and is non-standard in appearance, therefore did not become popular with typical bicycle consumers.
United Kingdom Patent No. 2138755, which is hereby incorporated by reference, discloses a plastic handlebar with grip portions in a non-standard loop shape, and which requires non-standard brake levers, also to the dissatisfaction of typical bicycle consumers.
The Rafac, Robinson and U.K. patent handlebars discussed above are all made by injection molding of thermoplastics with or without discontinuous reinforcing fibers. The injection molding methods used are those typical in the art for molding shapes with a low to moderate length to width ratio (aspect ratio), thus in part accounting for their unusual shapes.
For additional general reference material, the reader is directed to U.S. Pat. Nos. 2,114,733, 2,487,661, 3,039,791, 3,533,643, 3,833,242, 4,008,903, 4,015,854, 4,067,589 4,322,087, 4,548,422, 4,550,927, 4,565,383, 4,596,398, 4,828,285, 4,901,209, 4,923,203, 5,011,172, 5,016,895 each of which is hereby incorporated by reference for the material disclosed therein.
There are also a number of composite handlebars in the commercial prior art which are made by methods including table rolling of resin-impregnated fabrics and tapes, and filament winding. These methods produce handlebars which are too costly to result in widespread use.
Due to the deficiencies of the prior art, there is a need for a handlebar which has the advantages of plastic or fiber-reinforced plastic material, such as light weight, inherent shock absorption characteristics, and low cost manufacture, but that has similar outward appearance, configuration and attachment means as a standard prior art metal handlebars in appearance, shape, configuration, and attachment means. The prior art also lacks a method for making such a fiber-reinforced plastic handlebar from an injection molding process.